What are those sessions? Are they Application connections? If they are
application connections, you can probably kill them if there are no bad
side effects. Not sure of how your applications connect or reconnect
when a session dies.

Tom

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I have an issue with dropping undo tablespace. I am running Oracle 9i on
Solaris 9. On one of our production database, our UNDO tablespace
datafiles have autoextend ON, so they have increased in size to about
30G now and have filled up the file system. To get around this problem,
i have created a new UNDO tablespace and switched the database to use
this 2nd UNDO tablespace. The undo_retention is set to 7200 (sec). It
has already been 2 days since i performed the switch and my alert log is
still being flooded with " Undo Tablespace 1 Moved to Pending Switch-Out
state" . Following is detailed process that i followed,

I have getting this from previous two days. I gone through the metalink
id: 341372.1 that speaks about this Switch out state and gave two
queries to find as what transactions are currently using the Undo
tablespace. Following is the output from these two queries,

4 _SYSSMU4$ PENDING OFFLINE 34 2121 00000001E1006928
It has been almost 2 days these 3 transactions have started and still
running. I wanted to drop the first UNDO tablespace ones all
transactions have been completed and all segments are offline but these
3 transactions are preventing this. The only option i see here is to
kill the session (22,16,34), which will offline all the undo segments
and then drop the first undo tablespace. This is a production box, so
just wanted to confirm with you. Is it safe to go ahead and kill the
session? is there any other work around in this case for dropping the
first undo tablespace.